Nov. 11, 2009 -- Workers exposed to very high levels of the chemical bisphenol A (BPA) were four to seven times more likely to report sexual function problems than were workers with no occupational exposure to the chemical, a new study shows.

Earlier research has linked BPA exposure to reproduction problems in animals, but the five-year study is the first to do so in humans.

Researchers with Kaiser Permanente compared self-reported sexual function scores among male factory workers in China who were and were not exposed to BPA on the job.

BPA levels among the occupationally exposed men were about 50 times higher than average levels among American men and Chinese men with no occupational exposure to the chemical, the researchers say.

Lower Sex Drive, Less Satisfaction

Compared to the unexposed factory workers in the study, BPA-exposed workers were four times more likely to report erectile dysfunction, low sexual desire, and less than optimal satisfaction with their sex lives. They were seven times more likely to report problems with ejaculation.

The findings must be replicated to prove the link between high levels of exposure to BPA and sexual dysfunction in men, Kaiser Permanente reproductive epidemiologist De-Kun Li, MD, PhD, tells WebMD.

"We also need to study lower levels of exposure closer to those consumers get," he says. "But up until this point the critics have dismissed the idea that BPA has health effects at any level because most of the research has been in animals. They can no longer do this."

BPA has been used for more than three decades to make plastic bottles and other products shatter resistant and clear. It is also used in the lining of many canned foods and a wide range of other commercial goods.

For nearly a decade, scientists have debated whether exposure to BPA through commercial products poses a health threat to humans.

The new study, published in the journal Human Reproduction, does not address this issue because BPA levels among the occupationally exposed men were so much higher than in the community at large.

Consumer BPA Risk Debated

But Kathy Gerwig, Kaiser Permanente vice president for workplace safety and environmental stewardship officer, says because it is not clear what constitutes a safe level of exposure to the chemical, consumers should seek products that are BPA-free.

“More research is definitely needed to explore the effects of BPA at lower levels, but it is certainly concerning that at the occupational levels reported in this study there is now evidence that PBA has harmful effects on the male reproductive system,” she tells WebMD.

Last spring, the six largest manufacturers of baby bottles announced they would stop making bottles containing BPA for sale in the United States.

And more and more of those rigid reusable plastic water bottles sold in stores are now made without BPA and have labels telling consumers this.

But there is little way of knowing if the canned foods you buy contain BPA in their linings because few manufacturers say so on the labels.

Gerwig expects that to change as more consumers demand BPA-free products.

American Chemical Council spokesman Steve Hentges, PhD, tells WebMD the new study has little relevance to the public at large because BPA levels among the exposed workers were so much higher than normal.

He points out that the study was relatively small, with just 230 occupationally exposed and 404 unexposed workers, and it relied on self-reported observations of sexual dysfunction.

“It is interesting information, but is of little relevance to the average consumer using products with trace levels of BPA,” he says. “Based on the findings of the many government agencies that have examined the science, there is a consensus that BPA poses little risk to human health at these levels.”